|Year : 2015 | Volume
| Issue : 1 | Page : 32-34
Epidermal inclusion cyst in the neck masquerading as a thyroid neoplasm
Subramanian Kannan1, L Akila2, Murugan Kuppuswamy3, Naveen Hedne4
1 Department of Endocrinology, Diabetes and Bariatric Medicine, Narayana Health City, Bangalore, Karnataka, India
2 Department of Pathology, Narayana Health City, Bangalore, Karnataka, India
3 Department of Radiology, Narayana Health City, Bangalore, Karnataka, India
4 Department of Head and Neck Oncology, Narayana Health City, Bangalore, Karnataka, India
|Date of Web Publication||18-Dec-2014|
Dr. Subramanian Kannan
258/A Bommasandra Industrial Complex, Narayana Health City, Bangalore - 560 076, Karnataka
Source of Support: None, Conflict of Interest: None
A number of non-thyroidal masses can mimic thyroid nodules. A through preoperative work-up is crucial to help differentiate the origin of the mass which is useful in planning surgical intervention and avoid any iatrogenic damage to the thyroid gland. We present a case of a neck mass in a 24 year male clinically mimicking a thyroid neoplasm. Careful preoperative imaging and fine needle aspiration suggested the non-thyroidal origin of the mass. Complete surgical excision of the mass revealed the final pathology as an epidermal inclusion cyst.
Keywords: Epidermal inclusion cyst, thyroid, neck mass
|How to cite this article:|
Kannan S, Akila L, Kuppuswamy M, Hedne N. Epidermal inclusion cyst in the neck masquerading as a thyroid neoplasm. Thyroid Res Pract 2015;12:32-4
|How to cite this URL:|
Kannan S, Akila L, Kuppuswamy M, Hedne N. Epidermal inclusion cyst in the neck masquerading as a thyroid neoplasm. Thyroid Res Pract [serial online] 2015 [cited 2020 Jan 17];12:32-4. Available from: http://www.thetrp.net/text.asp?2015/12/1/32/147290
| Introduction|| |
Midline neck masses including pre-tracheal lymph nodes, thyroglossal cyst, epidermal inclusion cyst, dermoid cyst can mimic a thyroid nodule. Epidermal inclusion cysts, or epidermoid cysts, are uncommon but not rare lesions when encountered in the head and neck region. They are included in the spectrum of teratomas which also encompasses dermoid cysts and teratoid cysts. Epidermoid cysts are less common than dermoid cysts; they tend to occur along the midline and may mimic other congenital lesions thereby presenting a diagnostic challenge when encountered on imaging studies. Distinction between these non-thyroidal masses and thyroid nodule requires imaging and in most cases surgical resection. We present a case of a midline neck mass in a 24 year male which turned out to be an epidermal inclusion cyst and discuss the preoperative imaging and biopsy findings which aided in appropriate surgical resection.
| Case Report|| |
24 year male presented with a painless swelling in front of the neck for the past 10 years. He noted that there was no rapid increase or decrease in the size of the swelling nor was there any pain or discomfort. He denied any compressive symptoms and symptoms related to hypo or hyperthyroidism. On examination, patient had a 4 × 2 cm lobulated mass in the region of the thyroid isthmus and extending into left side of the neck [Figure 1]. The swelling moved with deglutition but not with protrusion of tongue. No significant lymph nodes were palpable. Rests of his clinical examination including his vital signs were normal. Lab tests revealed normal TSH 1.21 mIU/L and negative thyroid peroxidase (TPO) antibodies (<28 IU/L). Neck ultrasonography showed a well-defined 4 (L) ×3.5 (AP) ×2 (W) cm homogenous mass, isoechoic to thyroid parenchyma with a clear margin of delineation between the mass and the thyroid with no vascular flow [Figure 2]. It was unclear whether the nodule was arising from the left thyroid lobe or was an extra-thyroidal swelling. Fine needle aspirate (FNA) of the mass showed inspissated debris like material which on microscopy showed predominantly anucleate squamous cells and a few nucleated squamous cells [Figure 3]. No thyroid follicular epithelial cell clusters were seen. Computed tomography (CT) scan of the neck was performed which showed the mass to be anterior to the thyroid gland with pre-contrast attenuation of 68 HU with a small pocket of air consistent with previous FNA [Figure 4]. Patient underwent a diagnostic surgical excision of the mass. Gross pathology revealed a cystic structure with smooth lining measuring 3 × 3 × 2 cm filled with yellow soft putty material. Microscopy revealed a cyst lined by benign stratified squamous epithelium [Figure 5]. The wall of the cyst was formed by fibrocollagenous tissue with chronic inflammatory infiltrate and foreign body granuloma formation. No adnexal structures, hair shafts or thyroid tissue were identified in multiple sections examined. These features were consistent with an epidermal inclusion cyst.
|Figure 1: Neck mass on inspection a 4 × 2 cm, oval shaped lobulated mass in the midline and extending towards the left side of the neck|
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|Figure 2: Ultrasound images of the lesion (sagittal view-a) showing an iso-echoic, avascular (b) mass in the midline and extending to the left and anterior to the left lobe of the thyroid gland|
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|Figure 3: FNA of mass: Showing few scattered anucleate and nucleated squamous cells and no colloid or thyroid follicular epithelial cells (inset-higher magnification)|
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|Figure 5: Final HPE microscopy images showing cyst wall lined by benign stratified squamous cell epithelium resting on fibro-collagenous tissue wall|
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| Discussion|| |
Epidermal inclusion cyst (EIC) are rare in the neck area and when present in the anterior aspect of the neck, can mimic as a thyroid neoplasm. In the case presented, we had multiple clues to origin of the neck mass as an extra-thyroidal in origin. The ultrasound and CT of the neck clearly showed a distinct delineation of the mass and the thyroid and the mass was placed anterior to the thyroid. The ultrasound and CT images lacked the typical features of a cyst (hypoechoic and low attenuation) due to the densely packed keratinaceous material in the cyst. The final pathology was consistent with an EIC.
EIC arises from trapped ectoderm during the time of midline fusion of branchial arches  or due to iatrogenic inclusion of epidermal elements in the dermis. The development of EIC does not involve thyroglossal tract or tissues migrating around the hyoid bone, and thus does not move up with protrusion of tongue and does not necessitate hyoid resection (Sistrunk surgery). While EIC is a dermal cystic enclosure of keratinized squamous epithelium filled with keratin debris (elements derived from ectoderm), a dermoid cyst contains skin appendages including hair follicles, sebaceous glands (elements derived from ectoderm and mesoderm) and a teratomatous cyst contains elements from all three germ layers and contains tissue foreign to the neck. 
| Conclusion|| |
Midline neck masses can be extra-thyroidal in origin and careful preoperative imaging and FNA of the mass can help plan surgical resection and avoid damage to the thyroid.
| References|| |
Sullivan DP, Liberatore LA, April MM, Sassoon J, Ward RF. Epidermal inclusion cyst versus thyroglossal duct cyst: Sistrunk or not? Ann Otol Rhinol Laryngol 2001;110:340-4.
Baredes S, Lee HJ, Eloy JA. Radiology quiz case. Epidermal inclusion cyst with intracystic keratin debris. Arch Otolaryngol Head Neck Surg 2002;128:723-4.
[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]